Section 15 Base metals and articles of base metal 73 Articles of iron or steel 73 06 Other tubes, pipes and hollow profiles (for example, open seam or welded, riveted or similarly closed), of iron or steel. 73 06 50 Other, welded, of a circular cross-section, of other alloy steel Commodity Code Description 73 06 50 00 Other, welded, of a circular cross-section, of other alloy steel